Bone consists of inorganic minerals and organic substances. The inorganic minerals are formed from hydroxyapatite, Ca10(PO4)6(OH)2. The organic substances consist mainly of proteins, and the proteins consist mainly of collagen. To release phosphorus containing compounds e.g., phosphates, from bone, bone materials can be treated with acid in an aqueous medium, which solubilizes hydroxyapatite, resulting in the release of calcium (Ca2+) and phosphate (PO43−) ions into the aqueous medium (reaction equation 1). The presence of the bone protein matrix increases the amount of acid required, which increases both the size of the process equipment and the cost of mineral extraction, according to the following general reaction scheme.Ca10(PO4)6(OH)2+8H+→10Ca2++2H2O +6HPO42−  (1)
Phosphorus containing compounds such as phosphates are important, for example, tor producing agricultural fertilizers. Currently the manufacture of phosphorous fertilizer requires manufacturing of an acid and then reacting the acid with certain bases in order to generate at fertlizer salt, such as ammonium phosphate, potassium phosphate etc.
European patent application EP1964828B1 discloses is method of using certain bacteria to generate reduced forms of phosphorus, such as phosphites and/or hyposphosphites from inorganic materials, such as rock phosphate and soils. U.S. Pat. No. 6,464,875 describes fermenting animal by-products to produce ammonia and solid materials for fertilizer production. CN102020508A relates to preparing a fertilizer by fermenting with “phosphorus-solubilizing bacterium” e.g. donkey bone and other organic material. The process includes a pre-fermenting step wherein the organic material is hydrolysed with a strong base. U.S. Pat. No. 6,776,816 describes production of magnesium ammonium phosphate by fermenting manure.
Nevertheless, there remains a longstanding need in the art for improved processes for phosphate production from food production byproducts and agricultural waste.